Effluent gas stream treatment system having utility for oxidation treatment of semiconductor manufacturing effluent gases

ABSTRACT

An effluent gas stream treatment system for treatment of gaseous effluents such as waste gases from semiconductor manufacturing operations. The effluent gas stream treatment system comprises a pre-oxidation treatment unit, which may for example comprise a scrubber, an oxidation unit such an electrothermal oxidizer, and a post-oxidation treatment unit, such as a wet or dry scrubber. The effluent gas stream treatment system of the invention may utilize an integrated oxidizer, quench and wet scrubber assembly, for abatement of hazardous or otherwise undesired components from the effluent gas stream. Gas or liquid shrouding of gas streams in the treatment system may be provided by high efficiency inlet structures.

This application is a division of and claims priority to U.S. patentapplication Ser. No. 09/970,613, filed Oct. 4, 2001, now U.S. Pat. No.7,214,349, entitled “Effluent Gas Stream Treatment System Having UtilityFor Oxidation Treatment of Semiconductor Manufacturing Effluent Gases”which is a division of and claims priority to U.S. patent applicationSer. No. 09/400,662, filed Sep. 20, 1999, now U.S. Pat. No. 6,333,010which is a continuation of and claims priority to U.S. patentapplication Ser. No. 08/775,838, filed Dec. 31, 1996, now U.S. Pat. No.5,955,037. Each of these applications is hereby incorporated byreference herein in its entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates to a system for the treatment ofindustrial effluent fluids such as effluent gases produced insemiconductor manufacturing, photovoltaic processing, etc. Such systemmay variously include an oxidizer, gas scrubbing, particulate solidsremoval, and other unit operations for effluent gas treatment.

DESCRIPTION OF THE RELATED ART

In the treatment of industrial fluid waste streams, a wide variety ofunit operations and corresponding discrete treatment apparatus have beenintegrated for processing of the effluent from an upstream processfacility.

For example, various integrated thermal systems are commerciallyavailable for treatment of semiconductor manufacturing effluents andphotovoltaic processing off-gases. These integrated systems aretypically targeted for use with CVD, metal etch, etch and ion implanttools. Commercial integrated systems include the Delatech ControlledDecomposition Oxidizer (CDO), the Dunnschicht Anlagen Systeme (DAS)Escape system, and the Edwards Thermal Processing Unit (TPU). Each ofthese commercially available systems consists of an integration of athermal processing unit for oxidative decomposition of effluent gases,combined with a wet quench for temperature control of the off-gases fromthe hot oxidation section, and a wet scrubbing system for the removal ofacid gases and particulates formed in the oxidation process.

In the Delatech CDO, the thermal system comprises an electrically heatedtube which may optionally be combined with a flame-based insertableHydrogen Injection System (HIS) for the destruction of particularlydifficult-to-remove compounds from the effluent gas stream. In theaforementioned DAS Escape system, the thermal oxidizer is flame-based,using O₂ as the oxidizer and methane or hydrogen as the fuel. In theTPU, the thermal oxidizer comprises a flame-based surface combustionunit which uses air or O₂ as oxidizer and methane as a fuel.

In addition to these integrated commercial systems, there are alsovarious commercially available stand-alone single unit operationalsystems for the treatment of effluent gas streams, including: a)unheated physisorptive packed bed dry scrubbers, b) unheatedchemisorptive packed bed dry scrubbers, c) heated chemically reactingpacked bed dry scrubbers, d) heated catalytically reacting packed beddry scrubbers, e) wet scrubbers, and f) flame-based thermal treatmentunits. Each of these unit operation technologies is appropriate forcertain applications, depending on the nature of the gas streamundergoing treatment.

In general, each of these respective technologies is based on a distinctset of removal mechanisms for specific effluent stream constituents.These technologies can provide excellent abatement when either: a) theeffluent stream constituents requiring removal are sufficiently similarin removal mechanism pathway that a single removal technology caneliminate the gases of concern, or b) when the particular subset of gasstream constituent species that is not responsive to that particularremoval mechanism is of such character that the gas stream constituentspecies can be vented without abatement.

On occasion, the end user of the aforementioned stand-alone single unitoperationally-based systems may choose to combine two or more of thesevarious treatment units in order to provide a processing sequence foreach of the categories of the various gases being passed through thesystem. Nonetheless, the execution of such a consolidated equipmentapproach is clearly less convenient for the end user than for theoriginal equipment manufacturer, since the original equipmentmanufacturer can provide an integration of the various operationaltreatment units in a single small-sized treatment system in the firstinstance. The end user, by contrast, must substantially modify thecomponent stand-alone units for consolidated assembly and operation.

Additionally, while these original equipment manufacturer-integratedeffluent gas stream treatment systems clearly can, in certainapplications, have advantages over single unit operational systems,typically, these integrated systems, which may for example carry outunit operations of oxidation, quenching, and scrubbing, suffer fromvarious deficiencies, including: particulates clogging in the respectivesections as well as the inlet region of the oxidizer section, generationof particulates in the oxidation section, poor scrubbing of acid gasesin the scrubber section, high consumption of water for acid gas andparticulate scrubbing, and condensation of saturated off-gases from thescrubber section resulting in collection and concentration of aqueousmixtures with acids.

Inlet clogging can arise from several sources including: (a)back-migration of water vapor as combustion products of the oxidizersection, causing hydrolysis reactions in a, heterogeneous or homogeneousfashion with incoming water-sensitive gases such as BCl₃ or WF₆; (b)thermal degradation of incoming thermally-sensitive gases; and (c)condensation of incoming gases due to transition points in the system.These inlet clogging problems may require the incorporation of plungermechanisms or other solids removal means to keep the inlet free ofsolids accumulations, however these mechanical fixes add considerableexpense and labor to the system. In other instances, the inlet cloggingproblems may be systemic and require periodic preventative maintenanceto keep the inlet free of solids accumulations. Such maintenance,however, requires shut-down of the system and loss of productivity inthe manufacturing facility.

The existing integrated point of use gas effluent treatment systems mayalso experience problems in plant facilities which have difficulty intreating the wastewater from their wet scrubbing processes. A number ofplants may have difficulties processing the fluorine (F⁻) species in thewastewater generated from these point of use systems, or more generally,in processing wastewater deriving from the gas effluent treatment systemper se.

The water scrubber and quench portions of the integrated system can alsohave problems with clogging when quality of the feed water available tothe process facility is poor, a typical condition in the SouthwestUnited States. Lack of readily available water, high water costs, andhigh disposal costs for discharged wastewater are also significantproblems in many localities. In some cases, these factors necessitatethe use of high quality deionized water in the process facility toprevent clogging problems. While effective in preventing the scrubberand quench plugging, such solution involves a very high cost ofownership associated with the substantial costs of high qualitydeionized water.

In the scrubbing operation, poor scrubbing of acid gases in scrubbertowers can be due to the small flowrates that are processed throughthese systems. The diameters of scrubber towers processing such smallflowrates are correspondingly small, which when combined with the use ofconventional large diameter packing can result in a packing elementdiameter to column diameter which is excessively high and results inlarge wall effects in the scrubber tower. Such scrubber towers as aresult require large water flows, which in turn can cause channeling,flooding and slugging, with pockets of process gas passing untreatedthrough the scrubber system. Due to the poor scrubbing of these systems,corrosion in the ducting downstream of these systems is commonlyobserved, which is due to condensation of the untreated off-gases fromthe scrubber. When halide gases are being treated in the effluentstream, the off-gases from the scrubber tower will as a result of thepoor scrubbing performance of the scrubber contain unscrubbed halogencontent. The unscrubbed halogen content may result in formation of poolsof highly concentrated acids condensed at the VLE dewpoint condition,and a substantially higher than expected acid/water mix.

It is an object of the invention to provide an improved system for thetreatment of industrial effluent gases.

It is an object of the present invention to provide an improvedintegrated effluent processing system, utilizing water scrubbing andoxidation treatment of the effluent gas stream.

It is a further object of the invention to provide an improved systemfor the treatment of industrial effluent gases, which reduces thesusceptibility to clogging and solids accumulations in the system.

It is a still further object of the invention to provide an effluent gastreatment system utilizing water scrubbing, which substantially reducesthe water required in the scrubbing operation, relative to scrubbersystems of the prior art.

It is another object of the invention to provide such a system for thetreatment of effluent gases such as are produced in the manufacture ofsemiconductors, photovoltaic processing, and the like, which overcomethe above-discussed deficiencies of the prior art systems.

Other objects arm advantages will be more fully apparent from theensuing disclosure.

SUMMARY OF THE INVENTION

The present invention relates to an integrated effluent gas treatmentsystem, having utility for the point of use treatment of industrial gaseffluents, e.g., those produced in the manufacture of semiconductormaterials and devices.

In one aspect, the integrated effluent gas treatment system of thepresent invention is configured to include, for example in a unitaryhousing as a compact point of use device, some or all of the followingsystem components:

-   -   (i) a pre-treatment unit for acid gas and particulate removal        (e.g., a (pre)scrubber);    -   (ii) an electrothermal oxidizer or other oxidizer unit;    -   (iii) an oxidizer exhaust gas quenching unit;    -   (iv) an acid gas scrubber unit;    -   (v) gas flow-inducing means, such as an active motive flow means        (blower, fan, pump, etc.) or passive flow means (eductor,        ejector, aspiration nozzle, etc.); and    -   (vi) associated control means, which may for example include        influent gas temperature control means (e.g., including a        heat-traced foreline, heat exchanger; or other means for        ensuring appropriate thermal characteristics of the gas flowed        through the integrated system), power supply means (surge        protection, uninterruptable power supply (UPS) connection or        dedicated UPS components, etc.), and other process control        elements and subassemblies, for monitoring and selectively        adjusting the process conditions (temperatures, pressures, flow        rates, and compositions) in the system during its operation.

The integrated effluent gas treatment system of the present inventionmay utilize a pre-scrubber, oxidizers and scrubber assembly, incombination with a clog-resistant inlet structure for introducing afluid stream to the assembly from an upstream process facility.

Such clog-resistant inlet structure in one embodiment comprises firstand second generally vertically arranged flow passage sections in serialcoupled relationship to one another, defining in such serial coupledrelationship a generally vertical flow passage through which theparticulate solids-containing fluid stream may be flowed, from anupstream source of the particulate solids-containing fluid to adownstream fluid processing system arranged in fluid stream-receivingrelationship to the inlet structure.

The first flow passage section is an upper section of the inletstructure and includes an inner gas-permeable wall which may be formedof a porous metal or porous ceramic, or other suitable material ofconstruction, enclosing a first upper part of the flow passage. Thegas-permeable inner wall has an interior surface bounding the upper partof the flow passage.

The gas-permeable wall is enclosingly surrounded by an outer wall inspaced apart relationship to the gas-permeable inner wall. The outerwall is not porous in character, but is provided with a low pressure gasflow port. By such arrangement, there is formed between the respectiveinner gas-permeable wall and outer enclosing wall an interior annularvolume.

The low pressure gas flow port in turn may be coupled in flowrelationship to a source of low pressure gas for flowing such gas at apredetermined low rate, e.g., by suitable valve and control means, intothe interior annular volume, for subsequent flow of the low pressure gasfrom the interior annular volume into the flow passage. A high pressuregas flow port optionally may also be provided in the outer wall of thefirst flow passage section, coupled in flow relationship to a source ofhigh pressure gas for intermittent flowing of such gas into the interiorannular volume, such high pressure gas flow serving to clean the innergas-permeable wall of any particulates that may have deposited on theinner surface thereof (bounding the flow passage in the first flowpassage section). The high pressure gas may likewise be controllablyflowed at the desired pressure by suitable valve and control means.

The second flow passage section is serially coupled to the first flowpassage section, for flowing of particulate solids-containing fluiddownwardly into the second flow passage section from the first flowpassage section. The second flow passage includes an outer wall having aliquid injection port therein, which may be coupled with a source ofliquid such as water or other process liquid. The outer wall iscoupleable with the first flow passage section, such as by means ofmatable flanges on the respective outer walls of the first and secondflow passage sections. The second flow passage includes an inner weirwall in spaced apart relationship to the outer wall to define aninterior annular volume therebetween, with the inner weir wall extendingtoward but stopping short of the inner gas-permeable wall of the firstflow passage section, to provide a gap between such respective innerwalls of the first and second flow passage sections, defining a weir.When liquid is flowed into the interior annular volume between the outerwall of the second flow passage section and the inner wall thereof, theintroduced liquid overflows the weir and flows down the interior surfaceof the inner wall of the second flow passage section. Such tow of liquiddown the inner wall serves to wash any particulate solids from the walland to suppress the deposition or formation of solids on the interiorwall surface of the inner wall.

The flanged connection of the first and second flow passage sectionswith one another may include a quick-release clamp assembly, toaccommodate ready disassembly of the respective first and second flowpassage sections of the inlet structure.

Further, the first low passage section of the inlet structure may bejoined to an uppermost inlet structure quick-disconnect inlet section,which likewise may be readily disassembled for cleaning and maintenancepurposes.

In another aspect, the invention relates to an effluent gas treatmentsystem comprising a pre-scrubber for removal of acid gases andparticulates from the effluent gas, an oxidizer for oxidation treatmentof oxidizable components in the effluent gas stream and a subsequentwater scrubber for scrubbing the effluent gas stream subsequent tooxidation treatment thereof. In such pre-scrubbing/oxidation/scrubbingsystem, a gas/liquid interface structure may be employed, which isresistant to deposition of solids, clogging and corrosion, when a hot,particulate-laden gas stream containing corrosive components, asdischarged by the oxidizer, is received by such gas/liquid interfacestructure. Such gas/liquid interface structure comprises:

-   -   a first vertically extending inlet flow passage member defining        a first gas stream flow path therewithin, such inlet flow        passage member having an upper inlet for introduction of the gas        stream to the gas stream flow path and a tower exit end for        discharge of the gas stream therefrom subsequent to flow of the        gas stream through the gas stream flow path within the inlet        flow passage member;    -   a second flow passage member circumscribing the first flow        passage member and in outwardly spaced relationship thereto, to        define an annular volume therebetween, such second flow passage        member extending downwardly to a lower exit end below the lower        exit end of the first flow passage member, such second flow        passage member having an upper liquid-permeable portion located        above the lower exit end of the first flow passage member, and a        lower liquid-impermeable portion defining a gas stream flow path        of the second flow passage member;    -   an outer wall member enclosingly circumscribing the second flow        passage member and defining therewith an enclosed interior        annular volume; and    -   a liquid flow inlet port in such outer wall member for        introducing liquid into the enclosed interior annular volume        between the outer wall member and the second flow passage        member;    -   whereby liquid introduced via the liquid flow inlet port in the        outer wall member enters the enclosed interior annular volume        and weepingly flows through the upper liquid-permeable portion        of the second flow passage member, for subsequent flow down        interior surfaces of the liquid-impermeable portion of the        second flow passage member, to provide a downwardly flowing        liquid film an such interior surfaces of the liquid-impermeable        portion of the second flow passage member, to resist deposition        and accumulation of particulate solids thereon, and with the gas        stream flowed through the first flow passage member being        discharged at the lower exit end thereof, for flow through the        flow path of the second flow passage member, and subsequent        discharge from the gas/liquid interface structure.

By such arrangement, the gas stream is prevented from directlycontacting the walls in the lower portion of the structure, in which thegas stream flow path is bounded by the interior wall surfaces of thesecond flow passage member. The falling film of water from the “weepingweir” upper portion of the second flow passage member resistsparticulate solids accumulating on the interior wall surfaces of thesecond flow passage member. The motive liquid stream on such wallsurfaces cares the particulates in the gas stream contacting the waterfilm, downwardly for discharge from the gas/liquid interface structure.Additionally, corrosive species in the gas stream are prevented fromcontacting the wall, which is protected by the falling water film in thelower portion of the interface structure.

The upper liquid permeable portion of the second flow passage member maybe of suitable porous construction, and may comprise a porous sinteredmetal wall or a porous ceramic wall, with pore sizes which may forexample be in the range of from about 0.5 micron to about 30 microns, oreven larger pore-diameters.

Still another aspect of the present invention relates to a system forthe treatment of effluent gas streams, in which the system comprises apre-scrubber unit, an oxidizer/quench unit, and a scrubber unit, inwhich the pre-scrubber unit utilizes a counter-current gas/liquidcontact tower, wherein water flows downwardly from an upper portion ofthe tower and contacts gas introduced at a lower portion of the towersand in which the effluent gas stream is introduced via an inletstructure comprising a first tubular passage which is generallyhorizontally aligned and is concentrically arranged in relation to anouter circumscribing tubular member having a shield gas port forintroduction of shield gas thereinto. The inner tubular member receivingthe effluent gas terminates within the outer tubular member. The outertubular member extends generally horizontally into the lower portion ofthe pre-scrub tower, with the outer tubular member having a diagonallycut open end disposed in the lower portion of the pre-scrub tower. Thediagonally cut end of the outer tubular member is arranged so that themaximum length circumferential portion thereof is arranged todiametrically overlie the shortest length circumferential portion of theouter tubular member, so that the gas stream is discharged from theinner tubular member into the interior volume of the outer tubularmember and is discharged from the diagonally cut open end of the outertubular member into the lower portion of the pre-scrub tower. Bypositioning the maximum length circumferential portion of the outertubular member above the minimum length circumferential portion of theouter tubular member, the outer tubular member is arranged to preventdown-falling liquid in the pre-scrub tower from entering such tubularmember. Further, such arrangement of the diagonally cut end permits thegas flow stream being introduced to the pre-scrub tower to becomedeveloped at the point of its entry into the tower for contacting withthe down-falling liquid therein.

Additional aspects of the present invention may variously include thefollowing features:

-   -   1. The provision of a totally integrated gas effluent stream        treatment system in a unitary cabinet configuration including a        non-clogging inlet, pre-scrubber, oxidizer, wet/dry interface,        quench, post-scrubber and motive means.    -   2. The use of a pre-treatment subsystem for hydrogen fluoride        absorption. Such pre-treatment subsystem is in essence utilized        as a particulate pre-removal system by removing particulate        precursors rather than trying to remove fine particulates formed        during the oxidation process.    -   3. The provision of a wet/dry interface of a slit/hole injection        type or of a porous type interface, which can substantially        reduce water usage and render system leveling unnecessary.    -   4. The provision of a shell and tube heat exchanger type        oxidizer using radiative flux as a working “fluid” on tee shell        side.    -   5. The provision of sub-cooling in the water scrubber (together        with other features hereinafter more fully described) yielding a        condensationless or minimum-condensation design and enhanced        thermophoretic acid gas and particulate scrubbing; additionally        an ejector for fluid discharge may be employed to render the        effluent gas treatment system “invisible” to the exhaust line of        the processing system, or such discharge means may be employed        to increase the draw on the upstream process unit (e.g.,        semiconductor manufacturing tool) if necessary.    -   6. The use of a demister mesh as a packing element in the        scrubber column. Such demister mesh can substantially reduce        wall effects in scrubber columns of small diameter. Mass        transfer and heat transfer in the scrubber column as a result        are comparable to or better than scrubber column performance        with standard commercially available random packings, and        demister mesh-containing scrubber columns achieve relatively low        pressure drop. The void fraction at the top of the scrubber        column can also be flexibly designed to constitute the scrubber        column as a good particle collector; random packings are not as        flexible and do not readily permit the flexibility achievable        with demister mesh-containing scrubber columns.    -   7. The use of heat transfer enhancement inserts in the oxidizer        to tailor the effluent gas stream treatment system to        applications requiring varying thermal fluxes in the overall        operation of the system.    -   8. The recycle of a saturated H₂O/exhaust stream from the quench        of an oxidizer unit in the effluent gas treatment system to the        inlet of the oxidizer unit provides a low cost hydrogen source        for oxidation of perfluorocarbons (PFCs).    -   9. The addition of chemicals into the pre-scrubber may be        employed to alter the characteristics of the materials to be        scrubbed. An illustrative example is the addition of NH₃ to        tungsten hexafluoride effluent to form ammonium tungstate,        thereby yielding a material with elevated solubility for        scrubbing removal thereof.    -   10. The utilization of a transpiration tube reactor design for        the oxidizer unit to eliminate wall accumulations of        reactant/product solids in the oxidation step.    -   11. The use of a dual fluid atomizing nozzle in the quench unit        receiving the hot effluent stream from the oxidizer unit, in        order to minimize quench unit size, or the alternative use of        other small droplet atomizing means such as ultrasonic nozzles        or piezoelectric nozzles in the quench unit.    -   12. The integration of the gas effluent treatment system of the        present invention with specific semiconductor manufacturing        process tools.    -   13. The utilization of effluent gas introduction (inlet) means        to avoid clogging, as for example by deployment of the        anti-clogging inlet structure described more fully hereinafter.    -   14. The flexibility in the oxidizer unit to utilize electric or        flame (methane, propane, hydrogen, butane) based oxidation,        and/or the ability to use air or O₂.    -   15. The use of a wet scrubber or a dry scrubber as pre-scrubbing        and post-scrubbing means.    -   16. The use of a fluidized bed thermal oxidizer unit.    -   17. The use of a non-PFC-destructive PFC-recycle/recovery unit        in the effluent gas stream treatment system.    -   18. The provision of a clog-free oxidizer unit employing inserts        for disruption of the gas flow stream laminar boundary layer.

Other aspects, features and embodiments will be fully apparent from theensuing disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flowsheet of a gas effluent treatment system 10according to the invention.

FIG. 2 is a schematic flowsheet of a second portion of the gas effluenttreatment system 10 of FIG. 1 according to the invention.

FIG. 3 is a schematic flowsheet of a third portion of the gas effluenttreatment system 10 of FIG. 1 according to the invention.

FIG. 4 is a schematic flowsheet of a gas effluent treatment systemaccording to another embodiment of the invention.

FIG. 5 is a schematic flowsheet of a further effluent gas treatmentsystem embodiment of the invention.

FIG. 6 is a schematic flowsheet of a process system similar to thatillustrated in the FIG. 9 flowsheet, showing the modification thereof inaccordance with a further aspect of the invention.

FIGS. 7, 8 and 9 are respective schematic flowsheets according tofurther aspects of the invention.

FIG. 10 is a schematic flow sheet of a gas effluent treatment systemaccording to another embodiment of the invention) showing the gas/liquidinterface inlet structure associated with the pre-scrub tower.

FIG. 11 is a schematic representation of another gas effluent treatmentsystem according to the invention, schematically shown as beingcontained in a cabinet enclosure.

FIG. 12 is a schematic representation of a gas effluent treatment systemaccording to another embodiment of the invention, showing variousoptional ancillary features thereof.

FIG. 13 is a schematic representation of a clogging-resistant inletstructure according to an illustrative embodiment of the presentinvention.

FIG. 14 is a schematic cross-sectional elevation view of a gas/liquidinterface structure in accordance with another illustrative embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS THEREOF

The objective of the present invention is to provide an improved gaseffluent treatment system, which may be utilized to treat a wide varietyof effluent gas streams, deriving from correspondingly diverseindustrial processes.

In one aspect, the present invention contemplates a system for oxidationtreatment of an effluent gas stream deriving from an upstream processunit generating such effluent, in which oxidization and scrubbingprocesses are carded out, to abate hazardous or otherwise undesiredspecies in the effluent gas stream.

In a particular aspect, such effluent gas stream treatment system maycomprise oxidation and scrubbing unit operations, in which the system isconstructed and arranged to minimize the adverse effect of solidparticulates in the gas stream, such as may derive in the first instancefrom the upstream process, or which may be generated in-situ in theeffluent treatment system, e.g., as a result of the oxidation treatmentof the effluent gas stream, resulting in particulate reaction products.

The invention additionally relates to effluent gas treatment systems, inwhich gas/liquid interface structures are employed, to minimize adverseeffects of fluid hydrodynamic behavior, and to minimize particulatesolids accumulation and suppress clogging incident to the accumulationof solids in the system.

In another aspect, the present invention contemplates an integratedthermal treatment system which is competitive with, and superior to,other integrated thermal treatment systems on the market. Suchintegrated gas treatment system combines front-end thermal treatmentwith exhaust gas conditioning, and provides low cost of ownership to theend-user.

The integrated affluent gas stream treatment system of the invention mayutilize an electrically based thermal oxidation treatment unit. Whilethe ensuing description of the invention herein is primarily directed toeffluent gas stream treatment systems employing an electrical thermaltreatment unit, it will be recognized that the treatment system of theinvention could alternatively be configured to include other thermaltreatment components, e.g., flame-based treatment, fluidized bedtreatment, plasma treatment, etc.

By providing a flexible unit-operations based modular platform, theeffluent gas treatment system of the invention can be readily tailoredto a wide variety of effluent gas streams, e.g., semiconductorfabrication tool emissions, and may be readily modified to incorporateother unit operations treatment without undue effort.

The effluent gas stream treatment system of the present invention invarious embodiments thereof provides significant advantages over priorart treatment systems, including resistance to clogging within theconstituent effluent gas treatment units and associated flow piping andchannels, enhanced resistance to corrosion as a result of efficientgas/liquid interface structures, extended on-stream operating timebefore maintenance is required, low water usage rates when scrubbingtreatment is employed, superior scrubbing efficiency, with removallevels greater than 99.99% by weight of effluent scrubbable species, andreduction below TLV levels for halogen species such as HCl, Cl₂ and HF,oxidative destruction of hazardous species below TLV levels, eliminationof corrosive condensation of acids in process lines downstream of theoxidizer unit, flexible arrangement of constituent treatment units inthe effluent gas treatment system, and the capability for accommodatingmultiple sources of effluent gas from upstream process facilities.

Considering the oxidizer unit in the effluent gas treatment system ofthe invention, the oxidizer may utilize an electrical power source forelectrothermal oxidation of effluent gas species, or the oxidizer mayutilize fuel such as hydrogen and methane. If the system is arranged tocarry out destruction of perfluorocarbons in the oxidation treatment,the system may be arranged to utilize water vapor as an H⁺ radicalsource for effecting destruction of the perfluorocarbons. The oxidizermedium for such oxidation treatment may comprise air, oxygen, or otheroxygen-containing gas. In the quenching of the hot effluent gas streamfrom the oxidizer, and for scrubbing purposes, water may be employed forgas contacting, being dispersed for such contact by atomizer spraynozzles, or other suitable dispersers, which minimize droplet size andwater consumption in the operation of the effluent gas treatment system.In the treatment of streams from the oxidizer which contain significantquantities of silica particles, it may be desirable to utilize a causticsolution as a quench medium, to effect removal of the silica particles.

Relative to effluent gas treatment systems of the prior art, the systemof the present invention achieves various advantages in terms ofclogging resistance and corrosion resistance, minimization of water use,and flexibility in arrangement of effluent gas process units of thetreatment system in a compact, efficient conformation.

A pre-treatment unit may be employed in the effluent gas treatmentsystem of the invention to remove particulate and acid gases from theprocess stream before they get to the heated oxidation chamber and whilethey are at low temperature, thereby simplifying the duty requirementsof the downstream equipment.

While prior art systems may clog and require the introduction of specialunplugging mechanisms, the system of the present invention reliessubstantially on inherent fluid dynamics to prevent the system fromplugging in the first instance.

The effluent gas stream treatment system of the present invention may bearranged in a compact unitary cabinet having a suitable small footprint,so that the floor space area required by the cabinet in a processfacility is minimized.

When the effluent gas treatment system of the invention utilizes anoxidation unit for oxidizing species in the effluent gas stream, theoxidizer medium is preferably clean, dry air, although oxygen oroxygen-enriched air may be employed for such purpose, as well as anyother oxygen-containing gas of suitable character. The effluent gastreatment system of the present invention may be utilized for treatmentof a single upstream process unit generating effluent gas, oralternatively a plurality of effluent gas sources may be present, fromwhich the constituent effluent gas streams are consolidated into anoverall stream which is transported to the effluent gas treatment systemof the invention, for abatement of hazardous or otherwise undesirablecomponents of such gas stream, to yield a final effluent depleted insuch components.

In some instances, it may be desirable to operate in a time-varyingmode, if the composition of the effluent gas stream varies with time dueto differing effluent gas generating processes being carried out. Forexample, in semiconductor manufacturing, in the case of tungstenchemical vapor deposition (CVD), silane emissions may be generated inthe deposition step, and subsequent to such CVD operation, the CVDreactor may be cleaned, resulting in the production of NF₃ gaseouscomponents. Since silane derived from the CVD step would reactviolently, with NF₃ from the CVD reactor cleaning step, such gaseouscomponents cannot be mixed for unitary treatment, and therefore requireseparate processing in the effluent gas treatment system.

In the general practice of the present invention, the effluent gastreatment system may utilize a pre-treatment unit, in which the effluentgas is contacted with water to carry out a preliminary scrubbing step,upstream of oxidation treatment of the effluent stream. Suchpre-treatment therefore may involve scrubbing with water, oralternatively, such pre-treatment unit could employ a chemicalneutralization mixture for contacting with the effluent gas stream, andlikewise the effluent from the oxidation unit could be scrubbed usingwater or a chemical neutralization mixture. Accordingly, the scrubbingunit operations contemplated in the broad practice of the effluent gastreatment system of the present invention may utilize any suitablescrubbing medium, as appropriate to the specific gas stream beingprocessed. Alternatively, the scrubbing may be carried out as a dryscrubbing operation, rather than wet scrubbing. For such purpose, a widevariety of gas dry scrubber materials are readily commerciallyavailable, and may be employed for such purpose within the broadpractice of the present invention and the skill of the art. The scrubberunits employed in the practice of the present invention may be of anysuitable type, and may be constructed to minimize solids cloggingproblems in their operation.

The effluent gas treatment system of the present invention thus may bewidely varied in conformation and constituent treatment units. Suchconstituent treatment units may include an oxidizer which can be ofvarying type, such as a thermal oxidizer, catalytic oxidizer, flameoxidizer, transpirative oxidizer, or other process unit for effectingoxidation of oxidizable components within the effluent gas streamcomposition.

The effluent gas treatment system may also comprise a pretreatment unit,as mentioned, in which the effluent gas stream from the upstreamfacility is contacted with an aqueous medium or chemical neutralizationcomposition, or alternatively with a dry scrubber composition, to effectinitial abatement of some of the components in the effluent gas streamprior to subsequent oxidation and scrubbing treatment. The oxidationunit may be constructed and arranged to discharge hot effluent gas to aquench zone which may be integrated with a main scrubbing unit, ashereinafter more fully described, whereby the temperature of theeffluent gas from the oxidizer unit is markedly reduced for efficientsubsequent treatment. The unit may use a motive fluid means, either anactive means such as a pump, fan, compressor, turbine, etc., or apassive motive fluid driver such as an eductor, aspirator, or the like.

The effluent gas treatment system of the present invention may furtheremploy, in connection with use of aqueous media for scrubbing, variousneutralization processes, for removal of acidic components therefrom, orotherwise for achieving a desired pH level, for purposes of discharge ofwater from the effluent gas stream treatment system.

As a further variant, the effluent gas treatment system of the inventionmay flirter comprise a wet electrostatic precipitator for flume/plumecontrol, in the treatment of the effluent gas stream.

Various aspects of the design and construction of the effluent gastreatment system of the present invention are described below.

The oxidizer unit may be provided with suitable temperature controls andheat tracing, for temperature controlled operation of the oxidationunit.

The effluent gas pre-treatment unit may be arranged to remove as muchacid gas and particulates from the gas stream as possible before the gasstream enters the oxidation unit, thereby decreasing the dutyrequirement on downstream equipment. As mentioned, such pre-treatmentunit may comprise a wet scrubbing unit or alternatively a dry scrubbingunit, or a combination wet and dry scrubbing assembly comprisingconstituent wet and dry scrubbing units. Potentially useful wetscrubbing systems include wet cyclones, wet packed towers, and wet spraytowers. Such wet towers may operate in either co-current flow orcounter-current flow regimes.

The pre-treatment unit of the effluent gas treatment system may, forexample, comprise a wet spray tower which utilizes a nitrogen-assistedatomizing nozzle to introduce atomized scrubbing water at an upperportion of the tower. If chemical addition is desired, chemical mixingmay be carried out by use of such means as an in-line liquid-basedstatic mixer with appropriate chemical storage and metering.Nitrogen-assisted water atomization is advantageously employed tominimize water consumption of the effluent gas treatment system, and toprevent the effluent gas constituents from reacting with air upstream ofthe oxidation unit. The liquid from such wet processing unit operationsmay be drained to a common holding reservoir, which may be designed asan integral part of the scrubber/quench tower, as hereinafter more fullydescribed. As a further variation, the wet spray pre-treatment step maybe replaced by operation with a spray-fed venturi nozzle, to effect acidgas absorption and particulate removal.

Thus, the present invention in the provision of a wet scrubbing unitupstream of the oxidation unit provides the capability of controllingparticulate formation in the oxidation unit by scrubbing effluent gassteam components which are particle-forming agents under the conditionsexisting in the oxidation unit.

The oxidation unit as indicated hereinabove may be constructed with anysuitable configuration. For example, the oxidation unit may beconstituted by an electrothermal oxidizer utilizing a wrap-aroundclam-shell electric radiant heater having a large gap between the heatersurface and the heated tubes.

In a specific embodiment, the oxidation unit may comprise a singlevertical heated tube, with effluent gas being introduced through asparger, and with the effluent gas being blanketed in a nitrogen sheathto suppress reaction until the effluent gas is actually within theoxidation chamber. Once within the oxidation chamber, air or otheroxidizer medium may be injected to flow co-axially within the blanketedeffluent gas stream. The effluent gas introduction means are desirablyconstructed to closely simulate iso-kinetic laminar flow, to preventrecirculation zones, eddies, stagnation zones, and other anomalous flowbehavior, which could cause particle accumulation in operation of theoxidation unit.

The heated tube in such oxidation unit may be selectively controlled bysuitable thermal control means, to achieve desired operating temperatureregime. While minimum temperature conditions may be required to achieveignition and destruction of oxidizable components in the oxidation unit,excessively high temperatures may also promote particle agglomerationand accumulation on tube wall surfaces. Accordingly, the heated tubeoxidation unit may utilize heat transfer-enhancing tube inserts toprevent particle agglomeration on tube side walls, by promoting fluidflow transition to turbulence in the effluent gas stream being flowedthrough the oxidation unit.

Alternatively, the oxidation unit may comprise a bundle of heatexchanger tubes to accommodate higher gas stream flow velocities, andthereby suppress particle agglomeration on the wall surfaces of thetubes. In such heat exchange tube bundles, heat transfer enhancementinserts may be employed, as descried above in connection with the singlevertical heated tube configuration of the oxidation unit.

As a still further alternative, the oxidation unit may comprise amultiple bank of twisted tubes, which accommodate high gas streamvelocities and long residence times, while maximizing turbulentagglomeration of particles in the gas stream, via the provision of acontinuously spiraling gas flow path. Such arrangement may afford anincrease in particle size to a point where subsequent removal of solidsfrom the gas flow stream is readily carried out.

Materials of construction for the oxidation unit include any suitablematerials of construction, having due regard for the specific chemicalcomposition of the effluent gas stream being processed. Suitablematerials may include high temperature oxidation-resistant alloys, withgood resistance characteristics relative to HP and HCl. The oxidationunit may be operated in a reducing environment, to avoid destruction ofperfluorocarbon components, and suitable alloys may be employed asmaterials of construction to withstand such reducing conditions. In thisrespect, the effluent gas treatment system of the present invention mayutilize a unit for recovering the perfluorocarbon components of theeffluent gas stream, for recycling thereof or other disposition.

As a further variation, the oxidation unit may be constructed with anelectrically fired heater for heating of air or other oxidizer medium tohigh temperature for mixing with the effluent gas stream. Sucharrangement may in some instances provide self-ignition of oxidizablecomponents in the effluent gas stream, upon contact and mixing with theoxidizer medium, and this may increase the overall oxidation efficiencyof the oxidation unit.

As yet another variation, the oxidation unit may be constructed as atranspirative oxidation unit.

The oxidation unit produces an oxidized effluent gas stream which is atelevated temperature. Such hot stream is therefore subjected to quenchor cooling, to reduce the temperature for subsequent processing andfinal discharge from the effluent gas treatment system.

The effluent gas treatment system may therefore comprise a quench unitdownstream of the oxidation unit. The quench unit may for examplecomprise a single vertical tube with an air-assisted water atomizingnozzle, for contacting water or other quench medium with the hoteffluent gas from the oxidation unit. An overflow weir interfacestructure may be provided in the quench section, to provide awell-defined hot/cold interface. The quench unit may be constructed froma suitable alloy such as a dewpoint corrosion-resistant allow. Examplesinclude Al6XN, Carpenter 20, HaC-22 and HaB alloys. The quench unit isdesirably constructed to minimize adverse thermal effects on otherprocess units of the effluent gas treatment system.

The quench unit alternatively may comprise a multi-tube co-flow fallingfilm acid absorption column with a shelf-side chilled water supply toeffect heat transfer.

The oxidation unit and quench unit may be aligned in a single verticalorientation to provide a unitary linear gas flow path which minimizesanomalous flow behavior and particle accumulation.

As a still further alternative, the quench unit may be constituted by aspray-fed venturi quench apparatus for quenching and particle removalpurposes.

The effluent gas treatment system of the present invention may utilize ascrubber downstream of the oxidation unit. Such scrubber may comprise asingle vertical packed tower, with a liquid injection manifold on top ofthe column of packing, and a demister pad or other demisting meansthereover. The scrubber may be fed with liquid feed water, which may bechilled or at appropriate temperature, in relation to the effluent gasdischarged from the oxidation unit and optionally subjected to quenchingor preliminary cooling upstream of the scrubber. The scrubber maytherefore incorporate a chiller which can stand next to the scrubbertower and pre-chill the scrubbing water or other aqueous scrubbingmedium. In lieu of the use of demister pads or similar mechanical meansfor minimizing or eliminating residual mist (small size water droplets),scrubber units in the practice of the invention may be constructed tohydrodynamically minimize or substantially eliminate such mist componentby subjecting the gas stream to contact with larger droplet water“knock-down” sprays to remove the mist component from the gas stream.

The use of chilled water in scrubbing is desirable, to chill theeffluent gas stream to below ambient temperature, to thereby reduce thequantity of water vapor below prevailing ambient relative humidityconditions, e.g., in the environment of the semiconductor manufacturingoperation, when the effluent gas stream derives from a semiconductormanufacturing tool. The use of chilled water is also desirable tointroduce a thermophoretic effect to enhance acid gas absorption andparticulate absorption in the packed column.

An alternative scrubber unit comprises a falling film acid absorptioncolumn with chilled water feeding a shell-side of the absorption column.With such scrubber unit, liquid from the pre-treatment unit, thequencher, and the scrubber unit may be channeled to drain into a commonreservoir on the bottom of the scrubber column. In such manner, the usedliquid streams from the effluent gas treatment system are consolidated,and such reservoir may be arranged for gravity feed operation thereof.

Alternatively, the scrubbing liquid and other liquid streams from theconstituent process units in the effluent gas treatment system may bepressurized or discharged from the system by suitable pumping means,such as a centrifugal pump, peristaltic pump, air-driven pump, water-fedeductor, or other suitable liquid motive driver means.

In a packed column scrubber, a demister may be employed. The scrubbercolumn, as with other components of the effluent gas treatment system,may be formed of any suitable materials, such as metal alloys, or coatedstructural-steel or other metals, having coatings of appropriateresistant character relative to corrosive species in the fluid streamsbeing processed therein.

The effluent gas treatment system of the present invention may beconstructed either with or without provision for recirculation of usedliquid steams. As mentioned, the scrubber unit may comprise a dryscrubber, and it may be feasible in some instances to replace thescrubber unit and quencher unit with a dry scrubber cartridge unit. Thescrubber may also be provided with an optional chemical pre-treatmentunit, to allow the use of wet or dry chemical injection to the scrubberunit.

An eductor may be employed to provide motive force to draw the effluentgas stream through the effluent gas treatment system. Such eductorpreferably is of a corrosion-resistant and plug-resistant design,utilizing clean, dry air or other eduction fluid, with a modulatingvalve and control to provide appropriate inlet pressure to the effluentgas treatment system at a desired pressure level. The eductor may alsobe employed to supply a stream of heated dry air to the watervapor-saturated exhaust stream from the water scrubber when employed inthe treatment system. Such provision of heated dry air thus serves tolower the relative humidity of the effluent gas stream below ambientsaturated conditions. The eductor may utilize air, nitrogen or othersuitable educting medium.

The eductor may also be coupled with a suitable filtration module, topermit filtration of the eductor discharge; for capture of fineparticulates in such discharged gas.

The effluent gas treatment system of the present invention may beutilized for processing of effluent gas streams from a wide variety ofupstream process facilities. For example, the effluent gas processed inthe effluent gas treatment system may comprise effluent from a tungstenCVD tool of a semiconductor manufacturing plant in which wafers areprocessed to deposit tungsten thereon, with subsequent cleaning of thetool to remove excess tungsten deposits from chamber walls, pedestalelements, and electrodes of the tool assembly.

It will be appreciated that a wide variety of chemistries and effluentsmay be generated in the operation of a semiconductor manufacturingfacility, and that the construction, arrangement and operation of theeffluent gas treatment system of the invention may be widely varied toeffect treatment of the gas discharged from the tools and manufacturingoperations of the upstream process facility.

Referring now to the drawings, FIGS. 1-3 are consecutive sections of aschematic flowsheet for a gas effluent treatment system 10 according toone embodiment of the invention, showing in dashed line representationin FIG. 3 a variation of the flowsheet for a gas effluent treatmentsystem according to another embodiment of the invention.

In the ensuing disclosure, valves, instrumentation and ancillary controlmeans have been variously omitted for clarity, to facilitate thediscussion of the salient features of the invention, which has beenrendered in schematically illustrated form in the drawings for suchpurpose. It will be recognized that the valving, piping,instrumentation, and control means may be variously configured andimplemented in the broad practice of the present invention, within theskill of the art.

The FIG. 1 section of the flowsheet features a chilled water heatexchanger 12 containing a heat exchange passage 14 therein through whichchilled water is flowed from line 16 and is discharged in line 18.

Line 16 is joined to drain line 24 containing valve 26 therein. Lines 16and 18 may be suitably insulated to maximize the effectiveness of thechiller. Water in line 30 is flowed trough the chiller 12, and passed tomanifold line 32, from which the water is divided into two parts, withone part in line 34 being flowed through the system as shown, and theother part being passed in line 36 to the spray head 38 for introductionto the effluent gas stream pro-treatment column 40.

Effluent gas is introduced in line 62 and passed to the pre-treatmentcolumn 40. Line 62 may be insulated with heat tracing 64 along itlength, and the branch line 66, of insulated heat traced character, maypass to the next section of the flowsheet shown in FIG. 2.

Line 42 is an oxygen line for the process system, line 44 is a clean dryair line, and line 46 is a nitrogen supply line, which may as shownbranch to nitrogen feed line 47 for introducing nitrogen to the water inline 36 being flowed to the pretreatment column 40.

The effluent gas stream is introduced in line 62 to the column inletsection 50, and may be augmented by addition of nitrogen from branchline 48 if and to the extent desired. The effluent gas stream ispre-treated in the column 40 to produce a bottoms in line 60 which ispassed to the portion of the flowsheet in FIG. 3. The column at itsupper end 52 produces an overhead in line 68 which is passed to thereactor 90 in FIG. 2. A portion of the overhead may be recycled in line56 to the column, and further reflux may be accommodated by the line 58as shown.

In FIG. 2, the system 116 comprises the oxidation reactor 90 receivingnitrogen at its upper end from line 46, with oxygen in line 42 andoptionally clean dry air from line 44 from branch conduit 108 beingcombined to provide the oxygen-containing gas in line 110 which ispassed to the upper end of the reactor.

Water in line 34 is divided at the manifold 94 into branch line 96,passed to the section 120 of the system shown in FIG. 3, and into branchline 98, in which the fluid stream may be augmented by clean dry airfrom branch line 97 of line 44 and passed to nozzle 102 in oxidationreactor 90. The remainder of the clean dry air is flowed in line 112 tothe FIG. 3 portion of the process system.

The oxidation reactor is also arranged to receive water from line 100via inlet 92 at an intermediate portion of the reactor vessel. Thereactor features a reactor heater 88, comprising a heat exchange passage86 therein coupled with branch lines 82 and 84 of power line 80, bywhich the heater as is actuated to provide electrical resistance heatingof the reactor for thermal oxidation of the effluent gas streamintroduced in line 68 to the oxidation reactor. The oxidation reactormay be provided with recirculation line 106 interconnecting the upperand lower ends thereof as shown. Effluent from the reactor is flowed inline 104 to the FIG. 3 portion of the process system.

FIG. 3 comprises portion 120 of the process system and includes scrubber124 defining an interior volume 128 for scrubbing with water. Which isintroduced in line 96 to the nozzle 126. The effluent gas-stream isintroduced to the scrubber in line 104. The scrubber bottoms in line 132is joined with liquid from the effluent gas stream pre-treatment in line60, is discharged from the system, and is passed to waste watertreatment or other end use disposition of such liquid.

The scrubbed overhead is passed in line 130 to the eductor 144, which issupplied with clean dry air from line 112 to produce the treatmentsystem effluent, which is flowed in line 146 to the exhaust 150 asschematically shown. The effluent may be augmented by the additionthereto of bypass fume from line 66, and such line 66 may as mentionedbe heat-traced and insulated.

FIG. 3 shows a modification in dashed line representation, wherein pump136 is deployed to recycle the liquid bottoms in line 132 through inletpump line 138 to discharge liquid line 134, from which the recycleliquid is joined with the scrubbing water in line 96, to enhance thescrubbing operation by treatment of the recycle liquid therein. Treatedliquid then is discharged from the system in line 140 containing valve142 therein.

FIG. 4 is a schematic flowsheet of a gas effluent treatment systemaccording to another embodiment of the invention. In this system, thegas effluent stream is introduced in lines 160, 162, 164, and 166 andjoined to form the combined effluent gas stream in line 184, which thenis passed to heat exchanger 182 comprising heat exchange passage ISOjoined to line 178, to effect heat exchange of the consolidated stream.The heat exchanged effluent gas strewn then may be passed in line 212 tothe effluent gas stream pre-treatment column 210. Alternatively, a partor all of the effluent gas stream may be bypassed from the treatmentsystem and flowed in line 186 to the exhaust 256, if desired.

The chilled water heat exchanger 174 receives-chilled water feed in line168, and discharges the return chilling water in return line 172. Waterin line 170 passes through the chiller and is joined in line 224 withnitrogen in branch line 222 from main nitrogen feed line 216, and isdischarged in the pre-treatment column 210 via nozzle 226. Additionalnitrogen may be introduced to the pre-treatment column 210 in line 220from the main nitrogen feed line 216.

Clean dry air is introduced to the system in line 176, and a portionthereof may be passed in line 240 to the reactor 198 at an upper endthereof, together with nitrogen in line 216. Oxygen is introduced to thereactor in line 214. The reactor receives the overhead frompre-treatment column 210 in line 230. Power line 218 provides energy tothe electrical resistance heater 200 of the reactor 198 as shown.

The quench portion of the vessel containing oxidation reactor 198 at itsupper end, receives water from line 202 at inlet 208, and a mixture ofwater and clean dry air is introduced in line 204 to the nozzle 206 inthe quench portion of the vessel. The quench portion of the vesselcommunicates with the scrubber 194. The scrubber at its upper endreceives water from line 192 at nozzle 196.

Overhead gas from the scrubber is passed in line 250 to the eductor 252in line 250. The eductor receives clean dry air in line 259 from line240. The educted stream in line 254 then is joined with any bypassedeffluent gas from line 186 and is flowed in line 258 to the exhaust 256of the treatment system.

The bottoms from the effluent gas stream pre-treatment column 216 andthe bottoms from scrubber 194 in line 236, are joined in line 238 andmay be passed to waste liquid discharge or other treatment.

FIG. 5 is a schematic flowsheet of a further effluent gas treatmentsystem embodiment of the invention. The effluent gas stream isintroduced in line 312 to the pre-treatment column 308, together withnitrogen in line 310 and water in line 302 introduced via nozzle 306.The water steam to nozzle 306 may be augmented with recycled liquid fromline 304.

The pre-treatment column overhead in line 314 is passed to the oxidationreactor 334, which also receives oxygen in line 330 and nitrogen in line328. The vessel comprising reactor 334 is equipped with electricalresistance heater 332, and quench water is introduced to a lower quenchportion of the vessel 333 in line 324. Water or air/water mixture isinjected in the quench portion of the vessel 333 at nozzle 322 from line320, augmented if desired by recycle liquid from line 318.

The scrubber 336 discharges scrubbed gas in line 356, with scrubbingwater being flowed in line 344 and joined by treating chemical 340 fromvessel 338 pumped in line 341 by pump 342, to form the scrubbing liquidflowed in line 346 and joined with recycle liquid in line 348 to providescrubbing medium introduced to the scrubber 336 in nozzle 350. Bottomsfrom the scrubber is flowed in line 304 to the waste water heatexchanger 352 and heat exchanged with chilled water in line 354.

FIG. 6 is a schematic flowsheet of a process system similar to thatillustrated in the FIG. 9 flowsheet, showing the modification thereof inaccordance with a further aspect of the invention. In this FIG. 6embodiment, the scrubber 400 discharges scrubbed overhead in line 402,and bottoms in line 404. A portion of the bottoms liquid may be recycledin line 408, heat exchanged in heat exchanger 414 by chilled water inline 410, and used as make-up for the scrubbing liquid comprising waterintroduced in line 430 and heat exchanged in heat exchanger 416 bychilled water flowing through lines 412 and 418 of main line 410. Theresulting scrubbing liquid is further augmented by addition of liquidtreating chemical 422 from vessel 420 pumped from time 424 by pump 426to line 428 and joined with the scrubbing liquid from line 430 andpassed in line 406 to the nozzle in the scrubber 400.

FIGS. 7, 8 and 9 are respective schematic flowsheets according tofurther aspects of the invention.

In FIG. 7, the fume is introduced in line 442 to pre-treatment column438, along with water or water/nitrogen mixture in line 440, in whichthe fume is contacted with liquid from line 446, to produce overheadpassed in line 443 to the oxidation reactor 450. The reactor receivesoxygen in line 454 and nitrogen in line 452. The lower portion of thevessel containing reactor 450 is a quench section receiving recyclequench liquid in line 448, together with air in line 458 and water inline 456, for introduction in the quench section at nozzle 460.

The scrubber 464 is constructed as previously described, and receivesscrubbing liquid in line 478 from recycle line 472, deriving from thebottoms of the pre-treatment column in line 468 and the scrubber bottomscombined therewith in line 470 as shown. The recycle liquid in line 472may be heat exchanged in heat exchanger 472 by shined water in line 476.

The scrubbing liquid in line 478 may be augmented by addition thereto ofchemical liquid from line 494. The chemical liquid for such purpose ismade of water introduced to mixing vessel 4809 in line 482 and drychemical introduced to the vessel 430 in line 484. Alternatively, oradditionally, liquid chemical in vessel 486 may be pumped in line 498 bypump 490 to line 492 in which the liquid chemical may be diluted withwater introduced in such line. In this manner, the system shown in FIG.7 is adapted to utilize wet or dry chemical addition in the scrubbingliquid, as may be necessary or desirable in a given end use applicationof the treatment system of the invention.

In FIG. 8, the effluent gas stream is introduced in line 493 topre-treatment column 500, along with water or water/nitrogen mixture inline 496. A portion of such fluid may be diverted in line 504, combinedwith recycle liquid from line 506, and passed to the nozzle in thepre-treatment vessel.

In pre-treatment column 500, the effluent gas stream is contacted withliquid, to produce overhead passed in line 502 to the reactor 510. Thereactor receives oxygen in line 516 and nitrogen in line 518. The lowerportion of the vessel containing reactor 450 is a quench sectionreceiving recycle quench liquid in line 508, together with water inlines 512 and 514.

The scrubber 520 is constructed as previously described, and receivesscrubbing liquid in line 540 after it is heat exchanged in heatexchanger 538 by chilled water in line 530. The scrubber bottoms in line524 is combined with the pre-treatment column bottoms from line 526, andthe combined stream in line 529 may be passed to effluent waste liquidtreatment or other disposition, with a portion of the combined bottomsliquid being recycled in line 506. Scrubbed effluent gas overhead isdischarged from the scrubber in line 522.

In FIG. 9, the effluent gas stream is introduced in line 546 topre-treatment column 542, along with water or water/nitrogen mixture inline 544, in which the effluent gas stream is contacted with liquid fromline 548, to produce overhead passed in time 550 to the reactor 560. Thereactor receives oxygen in line 562 and nitrogen in line 564. The lowerportion of the vessel containing reactor 560 is a quench sectionreceiving recycle quench liquid in line 558, together with air in line556 and water in line 554, for introduction in the quench section at thenozzle interiorly disposed therein.

The scrubber 556 is constructed as previously described, and receivesscrubbing liquid in line 582 from recycle line 560, deriving from thebottoms of the pre-treatment column in line 552 and the scrubber bottomscombined therewith in line 558 as shown. The recycle liquid in line 560may be heat exchanged in heat exchanger 564 by chilled water in line568.

A portion of the chilled water in line 568 is withdrawn in line 570 andpassed to heat exchanger 590, for heat exchange with the waterintroduced in line 572. Chemical additive may be added from reservoir574 in line 576 under the action of pump 578, to augment the scrubbingwater in line 572, for subsequent combination with recycle liquid fromline 560, as mixed with the chemical/water solution in line 582 andsubsequently introduced to the nozzle at the upper end of the scrubber556. Scrubbing of the effluent gas stream thus is carried out to producea scrubbed overhead discharged from the scrubber in line 562.

FIG. 10 is a schematic representation of an effluent gas treatmentsystem according to yet another embodiment of the invention, utilizing apre-treatment unit, an oxidation unit, and a scrubber, wherein thescrubber and oxidation unit are coupled via a quench chamber.

The upstream process unit 602 discharges an effluent gas stream in line604 which enters inlet 606 of the effluent gas treatment system. Theinlet 606 is joined in gas flow communication with an inner tubularmember 608 having an open discharge end 610. The tubular member 608 isconcentrically arranged in outer tubular member 618, to provide aninterior annular volume 612 therebetween. The outer tubular member 618is provided with a gas inlet port 620 defied by tabular extension 622,to which gas from supply vessel 624 is suitably flowed to the tubularextension 622 in line 626 for flow through the interior annular volume612 between the inner and outer tubular members, so that the effluentgas steam discharged at open discharge end 610 of the inner tubularmember is sheathed in the gas supplied from gas supply 624.

For purposes of modulating the flow of gas from gas supply 624, line 626may contain a flow control valve or other flow control means foreffecting a predetermined flow rate of gas to the tubular extension 622.

The outer tubular member 618 of the inlet structure has a diagonally cutdischarge end 630, which is arranged so that the maximum lengthcircumferential portion of the outer cylindrical member 618 is above theminimum length circumferential portion of such tubular member. In thismanner, the maximum length circumferential portion serves as an“overhang” structure to permit development of the flow of the effluentgas stream, sheathed in the protective gas from gas supply 624, withoutpremature contacting of such sheathed effluent gas stream with thedown-falling liquid 632 in the pre-treatment tower 634.

Pre-treatment tower 634 is constructed as schematically shown, with alower sump reservoir 636 providing for collection and drainage inconduit 638 of scrubbing liquid from the tower. The tower is constructedwith an upper portion 640 in which is provided a spray nozzle 642 fedwith pre-scrub liquid from conduit 644 supplied from liquid supply 646and line 648 coupled to conduit 644. Line 648 may contain suitable flowcontrol valves or other means for modulating the flow of pre-scrubliquid to tower 634. Thus, the effluent gas stream from the upstreamprocess facility 602 is introduced through the inlet structure into thelower portion 650 of the tower 634, and countercurrently contacts thepre-scrub liquid 632 discharged from spray nozzle 642. The effluent gasstream thus is pre-scrubbed to remove particulates and acid componentsof the gas. The pre-scrubbed effluent gas then passes through the upperend of tower 634, passing through demister pad 652 to remove entrainedwater therefrom, with the demisted effluent gas mixture then passing inconduit 654 to the inlet unit 666, in which the conduit 654 isconcentrically arranged with respect to a larger concentric conduit 668communicating with plenum 670 receiving sheathing gas from gas source672 through line 674. The outer conduit 668 in turn is circumscribed bya plenum 676 receiving oxidant medium, such as air or otheroxygen-containing gas from oxidant medium supply 678 joined to plenum676 by line 680. The line 674 and 680 may contain flow control valves orother flow control means therein, for modulating the flow of therespective gases. By such inlet structure 666, the effluent gas streamenters in conduit 654, is sheathed in nitrogen or other inert gas fromsupply 672, and is co-currently introduced to the oxidizer unit 682 withoxidizer medium from plenum 676 deriving from supply 678.

The oxidation unit 682 may be a multi-zone oxidation reaction chamber,with the gas flow passage 684 defining gas flow path 686 therein,circumscribed by heater 698. The heater 688 may be an electrothermalunit, or comprise any other suitable heating means, whereby the gas ingas flow path 686 is heated to suitably high temperature to effectoxidation of the oxidizable components in the gas stream.

The oxidized effluent gas stream then passes in conduit 684 to a weepingweir gas/liquid interface structure 690 as described hereinafter ingreater detail. The weeping weir gas/liquid interface structure receivesliquid from liquid supply 692 via liquid feed line 694. The weeping weirgas/liquid interface acts to protect the lower walls of conduit 684 inproximity to the quench chamber 696, so that such interior wall surfacesof conduit 684 are isolated from hot, corrosive reaction products in theeffluent gas stream treated in oxidation unit 682. Concurrently, theweeping weir gas/liquid interface structure supplies a failing film ofwater on such interior wall surfaces of conduit 684 below the interfacestructure 690, to entrain particulates and prevent their accumulationand coalescence on the interior wall surfaces of conduit 684.

In quench chamber 696, quench air is flowed from quench air supply 698through line 700 to the quench chamber, concurrently with flow of quenchwater from water supply 702 through line 704 to mixing chamber 706, fromwhich the resulting air/water stream is discharged in quench chamber 696by nozzle 708, to effect quench cooling of the effluent gas stream.

The quenched effluent gas then flows into scrubber unit 710, from thelower portion 712 thereof to the upper portion 714 thereof, throughpacked bed 716 and demister pad 718, to produce a treated effluent gasstream which is discharged from the scrubber unit in overhead conduit720 under the action of eductor 722, or final discharge from theeffluent treatment system in discharge line 724.

The scrubber unit 710 has a spray nozzle 726 therein, supplied by feedconduit 728 with scrubbing medium from supply reservoir 730. Thescrubbing medium may be water or other aqueous medium, optionallyincluding chemical adjuvants for enhancing the scrubbing efficacy of thescrubber unit.

The quench chamber has a lower sump portion 750 for collection of quenchliquid and scrubbing liquid therein, and flow in discharge conduit 752to tank 754, which also receives bottoms liquid from the pre-treatmentunit in line 638. Such “bottoms liquid” from the process units in theeffluent treatment system may be treated in tank 754, such as byaddition of appropriate acid or base reagents in treatment tank 756,having ports 758, 760 and 762 for such purpose, whereby one or moretreatment chemicals may be added, subsequent to which final treatedliquid may be discharged from the system in discharge conduit 764.

FIG. 11 is a schematic representation of a treatment system according toanother embodiment of the present invention, schematically representedas being reposed within a cabinet 800.

The effluent gas stream treatment system of FIG. 11 features an effluentgas stream inlet conduit 802 receiving effluent from effluent feed line804 transporting the effluent gas stream from an upstream process unit806, such as a semiconductor manufacturing facility. The inlet conduit802 communicates with a gas shrouding structure 810 comprising acylindrical wall 812 having an inlet port 814 receiving gas fromreservoir 816 in line 818. The wall 812 defines with interior gaspermeable wall 820 an interior annular volume 822 from which gasintroduced from reservoir 816 flows through the gas permeable wall 820and shrouds the effluent gas flow stream being introduced from inletconduit 802. The effluent gas flow stream then flows downwardly througha first leg 824 of the pretreatment unit 826. The first leg 824 of thepre-treatment unit is provided with a spray nozzle 828 connected to afeed conduit 830 which in turn is joined to suitable sources of air andwater (not shown). In such manner, the downwardly flowing effluent gasstream is contacted with the air/water spray to pre-treat the gas aidreduce its acidity as well as to entrain particulates from the effluentgas stream in the aqueous phase being introduced from nozzle 828. Theresulting liquid then collects in the lower U-shaped portion 832 of thepre-treatment unit and flows by conduit 834 to sump 8363 communicatingwith sump 840 of the scrubber unit (hereafter more fully described) bymeans of the manifold conduit 842.

The effluent gas stream subsequent to contacting with the air/waterspray in the first leg of the pre-treatment unit then flows upwardlythrough the second leg 844 of such unit, in which the effluent gasstream is countercurrently contacted with down-falling water spray fromnozzle 846 coupled by conduit 848 to a suitable source of liquid, e.g.,water or other scrubbing medium (not shown). From the pre-treatment unit826, the pre-treated effluent gas stream passes in conduit 850 to thethermal oxidation unit 852, comprising effluent gas flow pipe 854,through the interior volume 856 of which the effluent gas stream isflowed while being heated to sufficient temperature to oxidize anddestruct deleterious oxidizable components of the gas stream. Theoxidized effluent gas stream then is discharged from the thermaloxidation unit 852 to the weeping weir gas/liquid interface structure860, as hereinafter more fully described, with the effluent gas streamthen flowing in conduit 862, which constitutes a quench chamber equippedwith feed port 864 for introduction of quench medium, such as water oran air/water spray, to the scrubber tower 870. The scrubber tower has alower portion 872 including a bottoms reservoir 874 which drainsaccumulated liquid through drainpipe 876 to the sump 840, from which theliquid may be drained via the manifold 842 and associated drainpipes.The scrubber tower 870 is provided with a scrubber medium spray nozzle878 at its upper portion, coupled via feed conduit 880 with a suitablesource of scrubbing medium (hot shown), which may comprise water orother aqueous or scrubbing medium. The scrubber tower suitably containsabove nozzle 878 a demister or other liquid disentrainment means (notshown), for reducing the moisture or liquid content of the scrubbed gas.The scrubbed gas rises to the upper end 890 of the scrubber tower and isdischarged in overhead conduit 892 through line 894, exteriorly of theeffluent treatment system cabinet 800.

By the arrangement shown in FIG. 11, the effluent gas stream receives abinary scrubbing treatment upstream of the thermal oxidizer unitfollowed by downstream scrubbing of the effluent gas stream dischargedfrom the thermal oxidation unit.

The thermal oxidizer unit may be of any suitable type, providingelevated temperature processing of the effluent gas stream, e.g., attemperatures up to 2000° F. or higher.

By providing the oxidation unit and the pre-treatment (i.e.,pre-oxidation treatment) scrubbing and post-oxidation scrubbing units ina single unitary cabinet, a compact apparatus conformation is provided,having a small footprint, accommodating the deployment of the effluentgas stream treatment system conveniently within a semiconductor fab, orother process facility in which the effluent gas stream being treated bythe system of the invention is located.

As mentioned, the scrubbing units in the effluent gas steam treatmentsystem of the present invention may be replaced by other wet or dryscrubbers or other treatment units for removing particulates and acidiccomponents, as well as other solubilizable or otherwise scrubbinglyremovable components from the effluent gas stream.

FIG. 12 is a schematic representation of a process system for treatmentof effluent gas from an upstream process 901, which enters cabinet 903in line 907 and is processed in treatment unit 905 for removal of acidiccomponents and removal of particulate solids. The gas stream treated intreatment unit 905 then is flowed in line 911 to the oxidation treatmentunit 913, in which the effluent gas stream is subjected to oxidationconditions for purification of the effluent gas stream by removingdeleterious or undesired oxidizable components of the gas stream. Theoxidized effluent gas then is flowed in line 915 to scrubbing unit 917for scrubbing treatment of the gas to produce a final treated gas streamwhich is discharged from the effluent treatment system in line 919,under the impetus of the motive fluid driver 921. As mentioned, themotive fluid driver may be an active device such as a fan, pump,turbine, compressor, etc., or a passive device such as an eductor,aspirator, or the like.

The FIG. 12 effluent treatment system may further comprise a quench unit923 for extracting the latent heat of the effluent gas stream subsequentto oxidation treatment thereof, and to cool the oxidation treatmenteffluent to an appropriate temperature for effective scrubbing in thescrubber unit 917.

The acidic components and particulates removal unit 905 may suitablycomprise a pre-treatment subsystem for hydrogen fluoride absorption,dedicated to removal of such component.

The inlets of the respective treatment units in the effluent treatmentsystem may suitably use wet/dry interface structures, such as aslit/hole inject type or porous type interface, to minimize water usagein the various treatment steps of the effluent treatment system.

The oxidation treatment unit 913 may comprise a shell and tube heatexchanger as the oxidation apparatus, which may utilize any suitableheating means or method. For example, radiative flux may be employed onthe shell side of the heat exchanger, to heat the effluent gas toappropriate temperature for oxidation of the oxidizable componentstherein.

The post-oxidation scrubbing unit 917 may incorporate heat exchangemeans for cooling of the gas to restrict condensation and enhance theefficacy of the scrubbing process. Scrubbing operations in the effluenttreatment system may be carried out in scrubber columns utilizing ademister mesh for de-entrainment of water in the scrubbed effluent gasstream. The overhead interior volume of the column may be provided as avoid volume for enhancing the removal of particulate solids from theeffluent gas stream.

As a further modification of the effluent gas stream treatment system ofthe present invention, the system may employ a halocarbon recovery unit927 for recovery of chlorofluorocarbons, perfluorocarbons, etc. Suchchloro/fluorocarbon recovery unit (CRU) may be constructed and operatedas disclosed in U.S. patent application Ser. No. 08/395,162 of Glenn M.Tom, et al., filed Feb. 27, 1995, now U.S. Pat. No. 5,622,682, for“METHOD AND APPARATUS FOR CONCENTRATION AND RECOVERY OF HALOCARBONS FROMEFFLUENT GAS STREAMS” and U.S. patent application Ser. No. 08/474,517 ofGlenn M. Tom, et al., filed Jun. 7, 1995 for ‘PROCESS FOR REMOVING ANDRECOVERING HALOCARBONS FROM EFFLUENT PROCESS STREAMS,” now abandoned,the disclosure of which hereby are incorporated herein by reference intheir entirety. The halocarbon recovery unit 927 thus may receiveeffluent gas in line 925 from line 911 subsequent to scrubbing or otherpre-oxidation treatment of the gas stream in treatment unit 905. Therecovered halocarbon then is discharged from the CRU unit 927 in line929, and may be recycled or otherwise utilized as desired. As a furtheralternative, the halocarbon may be recovered downstream of the oxidationtreatment of the effluent gas stream.

The oxidation treatment unit 913 may as indicated comprise a heatexchanger, and such heat exchanger may utilize heat transfer enhancinginserts in heat transfer passages thereof, as more fully described inU.S. patent application Ser. No. 08/602,134, filed Feb. 15, 1996 in thenames of Mark R. Holst, et al., now U.S. Pat. No. 5,914,091, for“POINT-OF-USE CATALYTIC OXIDATION APPARATUS AND METHOD OF TREATMENT OFVOC-CONTAINING GAS STREAMS,” the disclosure of which is herebyincorporated herein by reference in its entirety.

As a further modification if the effluent gas treatment systemschematically shown in FIG. 12, a saturated water/exhaust stream fromthe quench unit 923 may be recycled in line 931 to the inlet of theoxidation unit 913, to provide a low cost hydrogen source for oxidationof perfluorocarbons, if destruction of perfluorocarbons is desired,rather than recovery thereof.

The pre-oxidation unit 905 may comprise a pre-scrubber to whichchemicals may be introduced to alter the characteristics of materialsbeing scrubbed, e.g., addition of ammonia to tungsten hexafluorideeffluent, to yield ammonium tungstate. Ammonium tungstate has goodsolubility characteristics for scrubbing removal thereof.

The oxidation unit 913 may comprise a transportation tube reactor toeliminate wall accumulations of reactant/product solids in such step.

The quench unit 923 may utilize atomizing nozzles which employ multiplefluid inputs, e.g., of water and air or other gas, to reduce quench unitsize. Such quench unit alternatively may comprise atomizing means suchas ultrasonic nozzles, nebulizers, or petroelectric nozzles toeffectuate the quenching operation.

The oxidation unit 913 may utilize electric thermal oxidation, or mayotherwise affect oxidation through flame-based oxidation, as well as byany other suitable oxidation equipment and methods. The flame-basedoxidation unit may utilize any suitable fuel, e.g., methane, propane,hydrogen, butane, etc., and the oxidizing medium employed in theoxidation unit, generally may comprise air, oxygen, oxygen-enriched air,or any other oxygen-containing medium. The oxidation unit may alsocomprise a fluidized bed thermal oxidizer unit, within the broad scopeof practice of such treatment step.

As mentioned, the pre-oxidation treatment unit 905 and thepost-oxidation treatment unit 917 may comprise scrubbers of any suitabletype, wet as well as dry scrubbers, as well as any other suitablepre-oxidation and post-oxidation treatment means.

It will therefore be seen that the effluent gas stream treatment systemof the present invention is adapted to be embodied in a wide variety ofconstituent treatment component configurations, and that such treatmentunits may be compactly embodied in a unitary cabinet or housing, for usein a process facility such as a semiconductor manufacturing plant.

In general, the treatment system of the present invention contemplatesthe use of gas/liquid and gas/gas interface structures for “shrouding”the effluent gas stream with a circumscribing layer or sheath of gas orliquid. Such sheathing of the effluent gas stream may be desired, forexample to protect containing walls of gas flow passages, in relation tosolids accumulation and deposition which would occur in the absence ofsuch sheathing of the gas stream, as well as entrainment, particularlyin the case of sheathing liquid films, of particulates andsolubilization of deleterious components from the gas stream.

Accordingly, illustrative types of interface structures are describedhereafter, representing specific structural features and embodiments ofsuch approach.

FIG. 13 is a schematic representation of a clogging-resistant inletstructure according to an illustrative embodiment of the presentinvention, as usefully employed in the effluent gas stream treatmentsystem of the present invention.

The clogging-resistant inlet structure shown in FIG. 13 is connectableto process piping of the effluent gas stream treatment system, for acoupling such inlet structure with a source of the gas stream. Theprocess system piping upstream of such inlet structure may be suitablyheat-traced in a conventional manner, to add sufficient energy to thegas stream in the piping to prevent components of the gas stream fromcondensing or subliming in the inlet structure. It will be appreciatedthat any of the piping, conduits, flow passages or fluid-contactingstructure in the treatment system of the present invention may be heattraced, for such purpose, or otherwise to improve the performance of theprocess system.

The inlet structure 1060 shown in FIG. 13 comprises an inlet section1007 including an inlet flange 1016. The inlet flange is matablyengageable with the flange 1018 of upper annular section 1008 whichterminates at its upper end in such flange. The inlet section may becoupled with an upstream particulate solids-containing stream generatingfacility 1090, as for example a semiconductor manufacturing tool.

The annular section 1008 comprises an inner porous wall 1006 which is ofappropriate porosity to be gas-permeable in character, and an outersolid wall 1009 defining an annular interior volume 1020 therebetween.The interior surface of the inner porous wall 1006 thus bounds the flowpassage 1066 in the upper annular section 1008. The outer solid wall1009 at its upper and lower ends is enclosed in relation to the innerwall 1006, by means of the end walls 1040 and 1042 to enclose theannular interior volume. The outer wall 1009 is provided with a lowpressure gas inlet port 1022 to which is joined a low pressure gas feedline 1024. The low pressure gas feed line 1024 is connected at its outerend to a source 1004 of low pressure gas. A check valve 1014 is disposedin the low pressure gas feed line 1024, to accommodate the flow of lowpressure gas into the annular interior volume 1020. The feed line 1024may also be provided with other flow control means (not shown) forselectively feeding the low pressure gas from the source 1004 into theannular interior volume 1020 in a desired amount and at a desired flowrate, in the operation of the system.

The upper annular section 1008 also is provided with a high pressure gasinjection port 1050 to which is joined high pressure gas feed line 1052joined in turn to high pressure gas supply 1005. The gas feed line isshown with a flow control valve 1051 therein, which may be joined toflow controller means (not shown) for operating the flow control valve1051 in accordance with a predetermined sequence.

The upper annular section 1008 terminates at its lower end in a flange1026 which is matably engageable with flange 1028 of the lower annularsection 1030. The flanges 1026 and 1028 may be sealed by the provisionof a sealing means such as the O-ring 1010 shown in FIG. 13.

The lower annular section 1030 includes an outer wall 1012 terminatingat its upper end in the flange 1028. The outer wall at its lower end isjoined to the inner weir wall 1011 by means of the end wall 1044, toform an annular interior volume 1032 between the outer wall 1012 and theinner weir wall 1011. The inner weir wall 1011 extends verticallyupwardly as shown but terminates at an upper end 1046 in spaced relationto the lower end of inner porous wall 1006 of upper annular section1008, so as to form a gap 1036 therebetween defining an overflow weirfor the lower annular section 1030.

The outer wall 1012 of the lower annular section 1030 is provided with awater inlet port 1048 to which may be joined a water feed line 1080joined to water supply 1003 having liquid flow control valve 1081therein which may be operatively coupled with other flow control meansfor maintaining a desired flow rate of liquid to the lower annularsection 1030.

At its lower end, the lower annular section 1030 may be suitably joinedto the housing of the water scrubber 1013. The water scrubber may beconstructed in a conventional manner for conducting scrubbing abatementof particulates and solubilizable components of the process stream.Alternatively, the inlet structure 1060 may be coupled to any otherprocessing equipment for treatment or processing of the gas streampassed through the inlet structure, from the inlet end to the dischargeend thereof.

Thus, there is provided by the inlet structure 1060 a gas flow path 1066through which influent gas may flow in the direction indicated by arrow“1001” in FIG. 13 to the discharge end in the direction indicated byarrow “1002” in FIG. 13.

In operation, particulate solids-containing gas is introduced from anupstream source, such as a semiconductor manufacturing tool (not shown)by means of suitable connecting piping, which as mentioned hereinabovemay be heat-traced to suppress deleterious sublimation or condensationof gas stream components in the inlet structure. The stream enters theinlet structure 1060 in the flow direction indicated by arrow “1001” andpasses through the inlet section 1007 and enters the upper annularsection 1008. Low pressure gas, such as nitrogen, or other gas, isflowed from source 1004 through low pressure gas feed line 1024connected to port 1022, and enters the annular interior volume 1020.From the annular interior volume 1020 the introduced low pressure gasflows through the gas-permeable wall 1006, into the interior gas flowpassage 1066. The particulate-containing gas thus flows through theinterior gas flow passage 1066 and into the water scrubber 1013, as thelow pressure gas from gas feed line 1024 flows into the annular interiorvolume 1020 and through the gas-permeable wall 1006.

In this manner, the annular interior volume 1020 is pressurized with thelow pressure gas from the source 1004. Such pressure ensures a low,steady flow of the low pressure gas through the porous wall into theinterior gas flow passage 1066. Such low flow rate, steady flow of thegas through the gas-permeable wall maintains the particulates in the gasstream flowing through the interior gas flow passage 1066 away from theinterior wall surfaces of the inlet structure. Further, any gasespresent with the gas flow stream in the interior flow passage 1066 arelikewise kept away from the interior wall surfaces of the inletstructure.

The low pressure gas feed line 1024 can desired be heat traced. Suchheat tracing may be desirable if the gas stream flowing through theinlet structure contains species that may condense or sublimate anddeposit on the walls of the inlet structure.

Concurrently, high pressure gas from high pressure gas supply 1005 maybe periodically flowed through high pressure gas feed line 1052 throughhigh pressure gas injection port 1050 to the annular interior volume1020. For this purpose, the line 1052 may have a flow control valve (notshown) therein, to accommodate the pulsed introduction of the highpressure gas. In this manner, the high pressure gas is injected into theannular interior volume at specified or predetermined intervals, inorder to break away any particle buildup on the inner surface of the gaspermeable wall 1006. The duration and time sequencing of the pulsedintroduction of the high pressure gas may be readily determined withoutundue experimentation within the skill of the art, to achieve thedesired wall scouring effect which will prevent solids accumulation onthe gas permeable wall surfaces. If required, when the inlet structureis employed in connection with a water scrubber servicing asemiconductor manufacturing tool, such high pressure injections may beinterrupted during the tool batch cycle in order to eliminate pressurefluctuations at the tool exhaust port by suitable integration of controlmeans operatively linked to the tool control system. For this purpose, acontrol, valve such as a solenoid valve may be appropriately coupledwith control means of the tool assembly.

In the inlet structure embodiment shown, the flanges 1026 and 1028 maybe clamped to one another to permit quick disconnection of the upperannular section 1008 from the lower annular section 1030. For suchpurpose, a quick-disconnect clamp may be employed. The sealing gasket1010 between flanges 1026 and 1028 may be formed of a suitable materialsuch as a corrosion resistant, high temperature elastomer material. Thiselastomeric gasket additionally functions as a thermal barrier tominimize heat transfer from the upper annular section to the lowerannular section of the inlet structure, a feature which is particularlyimportant in heat traced embodiments of the invention.

The gas permeable wall 1006 of the upper annular section of the inletstructure may be formed of any suitable material, e.g., acorrosion-resistant Hastelloy 276 steel. The outer wall 1009 of theupper annular section may be a thin walled stainless steel pipe.

The lower annular section 1030 of the inlet structure may be formed ofany suitable material such as a polyvinylchloride plastic. Water isinjected into the annular interior volume 1032 between the outer wall1012 and the inner weir wall 1011 through line 1050 from water supply1003. Preferably, the water is injected tangentially, to allow theangular momentum of the water in the annular interior volume 1032 tocause the water to spiral over the top end 1046 of the weir wall 1011and down the interior surface of the weir wall in the interior flowpassage 1066 of the inlet structure. Such water flow down the interiorsurface of the weir wall 1011 is employed to wash any particulates downthe flow passage 1066 to the water scrubber 1014 below the inletstructure.

The pressure drop through the inlet structure can be readily determinedby pressure tapping the exhaust pipe from the upstream process unit andthe scrubber unit downstream of the inlet structure. The pressure dropcan be monitored with a photohelic gauge and such pressure drop readingcan be sent to suitable monitoring and control equipment to monitorclogging in the scrubber inlet.

By the use of the inlet structure in the system of the presentinvention, an interface may be provided between the water scrubber andthe tool exhaust stream from a semiconductor manufacturing operation,that does not clog repeatedly in normal process operation. Such inletstructure provides an interface with two ancillary process streams, asteady low flow purge stream and a high pressure pulse stream. The lowflow purge stream creates a net flux of inert gas, e.g., nitrogen, awayfrom the inner surface of the upper annular section toward thecenterline of the central flow passage 1066. The high pressure gas flowstream provides a self-cleaning capability against solids clogging. Thehigh pressure gas flow is employed to eliminate any particle buildup onthe inlet structure upper annular section interior surfaces of thecentral flow passage 1066.

Gases, entrained particles, and previously deposited particles are thendirected into the overflow stream at the inner wall surface in the lowerannular section of the inlet structure, to be flushed down into thewater scrubber downstream of the inlet structure. In this manner adirect interface between the gas permeable wall of the upper annularsection and the weir wall of the lower annular section of the inletstructure, providing a highly efficient inlet conformation whicheffectively minimizes the buildup of particulate solids in operation.

Such inlet structure has a number of advantages. In application to asemiconductor manufacturing facility and water scrubber treatment systemfor processing of waste gas effluents from a tool in the semiconductorprocess facility, the exhaust gas from the semiconductor tool can beheated continuously all the way from the tool exhaust port to the waterinterface in the water scrubber inlet structure. Heat tracing on theinlet lines can be used to heat the lines by conducting energy into thepiping, which transfers energy to the flowing gas stream by convection.Process gas may be heated all the way down to the overflow weir wall ofthe lower annular section of the inlet structure by heat tracing the lowpressure gas flow line which flows low pressure gas to the upper annularsection, as well as by heat tracing the high pressure gas flow linefeeding pulsed high pressure gas to the interior annular volume of theupper annular section of the inlet structure. Such flow of heated gaswill maintain the process gas flowing through the central flow passageof the inlet structure at a temperature which is determined by the vaporpressure of any particulate forming gas in the gas stream flowing to theinlet structure from the upstream process unit that would otherwisecondense or sublimate and deposit on the walls of the inlet structure.

Another advantage of the above-identified inlet structure is that suchstructure may be readily disassembled. In the event that the inletstructure does clog in operation, the structure is easily taken apart bysimply removing the clamps or other securement elements holding theflanges of the inlet structure to one another. The upper annular sectionmay thus be replaced by removing the clamps holding the respectiveflanges in position, and by disconnecting the respective gas feed linesthat feed the upper annular section.

A still further advantage of such inlet structure is that it isself-cleaning in character. Particles that have been entrained in thegas stream flowing to the inlet structure from the upstream process unitor that have been formed by chemical reaction in the inlet structure canbe readily cleaned from the gas-permeable wall of the inlet structure bythe pulsed high pressure gas injection into the interior annular volumein the upper annular section of the inlet structure. The particles thatare then dislodged from the interior wall surfaces of the upper annularsection of the inlet structure then are directed to the overflow portionof the weir wall where such particulate solids are flushed to thedownstream scrubber. The pressure, duration and periodicity of the highpressure gas pressure pulses can be easily set to accommodate theprevailing system particulate concentration conditions and character ofsuch solids. The effectiveness of the pulsed high pressure gas injectionwill depend on the character of the particulate solids. Such inletstructure therefore is self-cleaning in nature, without the use ofscraper or plunger devices typical of the so-called self-cleaningapparatus of prior aft fluid treatment systems.

The material specification of the porous wall element of the upperannular section of the inlet structure is dependent on the incomingprocess gas from the upstream process unit. If the gas stream includesacid gas components, such gases will be absorbed in the water scrubberand will be present in water which is recirculated to the overflow weirwall in the lower annular section of the inlet structure. It is possiblethat some of the overflow weir wall water will splash up on the porousinner wall of the upper annular section of the inlet structure. Theporous wall in such instance is desirably selected fromcorrosion-resistant materials of construction. A preferred metalmaterial for such purpose is Hastelloy 2776 steel, which exhibitsexcellent corrosion resistance under low temperature hydrous acidconditions.

Another advantage of the above-described inlet structure is that itminimizes the backflow of water vapor from the top of the water scrubberwhen the inlet structure is employed upstream of a water scrubber asillustratively described herein. By way of explanation of thisadvantage, it is to be appreciated that particulates may be present inthe exhaust streams of some semiconductor tools as either entrainedparticulates from the process tool or as the reactants of a chemicalreaction within the gas stream's flow path.

The reason for this particulate buildup is the occurrence of water vaporbackstreaming from the water scrubber downstream from the inletstructure. Water vapor released from the scrubber migrates back from thescrubber inlet toward the process tool, against the normal direction ofgas flow.

One mechanism involved in this back-migration of water vapor is gas-gasinterdiffusion. The only practical way of avoiding this source of watervapor back migration is to add a diffusion boundary to the waterscrubber inlet. Another mechanism for such back-diffusion of water vaporis the so-called Richardson annular effect. All dry pumps create acertain amount of pressure oscillation in the gas flow stream. Thesepressure oscillations create a counterflow transport mechanism thatpumps gases against the direction of normal gas flow. This phenomenon isa consequence of the boundary layer annular effect. Because of thiseffect, the backflow migration velocity is greatest a small distanceaway from the wall surface. The above-described inlet structureminimizes or eliminates the Richarson annular effect. Due to the steadyoutflow of low pressure gas at the inner surface of the porous wall ofthe upper annular section of the inlet structure, the static boundarylayer condition at the inner wall surface of the upper annular sectioncannot develop. There is a net flux of flowing gas from thegas-permeable wall which acts to “push” the process gas flow away fromthe wall bounding the central flow passage of the inlet structure, andavoids the presence of a static boundary condition, thereby avoiding theRichardson annular effect. Accordingly, if particles are formed as aresult of chemical reaction in the flow stream, the thus-formedparticles do not find a wall to agglomerate on. The particles insteadwill flow with the gas stream into the water scrubber. The same is truefor entrained particles. Once the particles reach the top of the inlet,they will become entrained in the gas flow stream because they will nothave a wall on which to collect.

By opposing the conditions which give rise to the Richardson annulareffect, the porous wall in the upper annular section of the inletstructure serves as an effective barrier to the back migration of watervapor to the exhaust lines of the process system. Any back migrationwill be exceedingly slow due to the aforementioned interdiffusionmechanism. This factor will greatly increase the mean time to failurefor the scrubber, since the scrubber entry and exhaust lines will notclog as often with the inlet structure of the present invention.

Although the porous wall member of the upper annular section of theinlet structure of the invention has been described herein as beingconstructed of a metal material, it will be appreciated that suchgas-permeable wall may be formed of any suitable material ofconstruction. For example, the porous wall may be formed of a porousceramic material having the capability to withstand the corrosiveatmospheres, temperature extremes, and input pressures that may bepresent in the use of the inlet structure of the present invention.

FIG. 14 is a schematic cross-sectional elevation view of a gas/liquidinterface structure which may be utilized in the practice of the presentinvention.

The gas/liquid interface structure 1110 includes a first verticallyextending inlet flow passage member 1112 defined by a cylindricalelongate wall 1114. The cylindrical wall 1114 circumscribes an enclosedflow passage 1118 within the inlet flow passage member 1112. At an upperend of cylindrical wall 1114 there is provided a radially outwardlyextending flange 1116 for joining the gas/liquid interface structure toassociated process flow piping, conduits, instrumentation, etc. Thefirst inlet flow passage member 1112 thus has an inlet 1120 at its upperend, and a corresponding outlet 1122 at its lower end, so that the openinlet and outlet ends define with the interior volume a flow pathincluding flow passage 1118, through which gas from an upstream processunit 1158 may be flowed, as in line 1160 illustratively shown in FIG.14.

The upstream process unit 1158 may for example comprise a semiconductormanufacturing tool and associated effluent gas treatment apparatus. Sucheffluent treatment apparatus may in turn comprise an oxidizer foroxidation of oxidizable components in the effluent gas. Suitableoxidizers are of widely varying type, and may for example be constitutedby a catalytic oxidation unit, a thermal oxidation unit, anelectrothermal oxidizer, etc.

When the upstream process unit 1158 comprises gas generating means andgas treatment means for semiconductor manufacturing operations, the gasstream introduced to inlet 1120 of the first inlet flow passage member1112 may be at elevated temperature and may contain substantialconcentration of particulate solids, e.g., in the form of sub-micronsize particles.

The interface structure 1110 further comprises a second flow passagemember 1124 which circumscribes the first flow passage member 1112 andis in spaced relationship thereto, as shown, to define an annular volume1130 therebetween. The second flow passage member 1124 extendsdownwardly to a lower end 1168 below the lower end of the first flowpassage member 1112, so that the open outlet 1122 of the first flowpassage member is in vertically spaced relationship to the open lowerend 1168 of the second flow passage member 1124.

The second flow passage member 1124 comprises an upper liquid-permeableportion 1126 elevationally above the lower end defining outlet 1122 ofthe first flow passage member, with a remaining liquid-impermeableportion 1128, extending downwardly from the liquid-permeable portion1126, as illustrated. The liquid-permeable upper portion 1126 and lowerliquid-impermeable portion 1128 may be formed in any suitable manner, asfor example by joining of an upper porous cylindrical segment 1126 to aninitially separate lower solid-walled cylindrical segment 1128, with therespective portions being joined to one another by brazing, soldering,welding, mechanical fastener securement, or in any other suitable mannerwith appropriate joining means and method. Alternatively, the secondflow passage member 1124 may be formed from a unitary cylindricaltubular member, an upper part of which is rendered liquid-permeable incharacter by processing, such as water-jet machining, etching,sintering, micro-electromachining, or any other suitable technique bywhich porosity or permeability characteristics can be imparted to theupper portion of such tubular member. Preferably, the second flowpassage member is formed of initially separate upper and lower portionswhich are joined together and wherein the upper portion is constitutedby a porous sintered metal matrix, or a porous ceramic material, whereinthe porosity is of sufficient dimensional character to allow liquidpermeation therethrough, as subsequently described hereafter in greaterdetail.

The gas/liquid interface structure 1110 further comprises an outer wallmember 1134 enclosingly circumscribing the second flow passage memberand defining therewith an enclosed interior annular volume 1170. Theouter wall member 1134 comprises a cylindrical side wall 1136, a top endwall 1138 and a bottom end wall 1140, which corporately enclose theinterior annular volume 1170. The side wall 1136 is provided with aliquid introduction port 1142. The port may be provided in any suitablemanner, but in the embodiment shown is constituted by tubular horizontalport extension 1144. Alternatively, the port may simply be an orifice oropening in the side wall, or other liquid inlet structure, wherebyliquid can be introduced into the interior annular volume 1170 from anexternal liquid supply.

In the FIG. 14 embodiment, the liquid inlet port 1142 is coupled withliquid introduction line 1146 containing flow control valve 1148therein. The liquid inlet line 1146 is connected to liquid supplyreservoir 1150.

The liquid flow control valve 1148 in line 1146 may be coupled tosuitable controller/timer means, including a central processing unit(CPU), microprocessor, flow control console, and/or ancillary monitoringand control means, for providing a predetermined or otherwise selectedflow of liquid from reservoir 1150 through line 1146 to liquid inletport 1142. The thus-introduced liquid fills the interior annular volume1170, and such liquid may be introduced at any suitable processconditions.

For processing of gas streams such as hot particulate-laden effluent gasstreams from semiconductor manufacturing operations, the liquid ininterior annular volume 1170 may be water or other aqueous media.

By virtue of the liquid-permeable character of the upper liquidpermeable portion 1126 of the second flow passage member 1124, liquidfrom interior annular volume 1170 permeates through the upper portion1126 of the second flow passage member and is expressed at the innerwall surface 1132 of such upper portion as liquid droplets 1154. Suchissuing liquid droplets, as a result of gravitational effect, fall andcoalesce with other liquid droplets and aggregate to form a downwardlyflowing liquid film 1156 on the inner wall surface 1172 of the lowerliquid-impermeable portion of the second flow passage member. The liquidin the liquid film discharging from the lower open end 1168 of thesecond flow passage member may be directed to suitable collection andprocessing means (not shown), e.g., for co-processing thereof in adownstream process unit 1164 to which the gas stream is flowed from gasflow passage 1152 of the second flow passage member in line 1162. Thedownstream process unit 1164 may be a water scrubber, reaction chamber,or other processing apparatus or treatment zone, in which the gas streamflowed from passage 1152 in line 1162 is subjected to other processoperations, with discharge of final effluent gas from the downstreamprocess unit in line 1166.

The gas/liquid interface structure 1110 thus is constructed to providean interior annular volume 1130 between the first and second flowpassage members, and with the first flow passage member 1112 extendingdownwardly below the liquid-permeable upper portion 1126 of the secondflow passage member, so that liquid weeping through the liquid-permeableupper portion can coalesce and develop the falling liquid film 1156. Bythis arrangement, the gas flowed from flow passage 1118 to flow passage1152 encounters an interior wall surface 1172 of the lower portion ofthe second flow passage member, which is blanketed with a protectiveliquid film 1156. Accordingly, any corrosive species in the gasdischarged from the lower open end 1122 of the first flow passage memberwill be “buffered” in relation to the inner wall surface, to minimizecorrosion and adverse reaction effects on such interior wall surface ofthe second flow passage member.

Further, by introduction of liquid to the interior annular volume 1170between the second flow passage member and the outer wall member 1134,there is provided a liquid reservoir “jacket” structure. Liquid therebyis provided to the porous upper portion of the second flow passagemember, for permeation therethrough, and downward “weeping” of liquid toform a protective film on the interior wall surface of the second flowpassage member.

Such falling film on interior surface 1172 of the second flow passagemember also serves to entrain and to carry away any particulates fromthe gas stream which in the absence of such liquid film might deposit onand aggregate on the interior wall surface of the second flow passagemember.

Accordingly, the falling liquid film affords a protective function withrespect to the interior wall surface of the second flow passage member,as well as an entrainment medium which carries away particulate solidsand any other gas phase components, which otherwise would be deleteriousin accumulation on the interior wall surface of the flow passage member.

As a further advantage of this structure illustratively shown in FIG.14, the use of a liquid permeable upper portion 1126 serves to minimizeliquid usage, relative to the provision of a structure such as a liquidoverflow weir, in which liquid from the interior annular volume 1170would simply overflow an upper end of wall 1126 and flow downwardly in afilm on the wall, over the full interior surface length of the secondflow passage member. The liquid required for operation thereby ismaintained at a very low level by the weeping weir structure of thepresent invention.

As an illustrative example of the implementation of the gas/liquidinterface structure illustratively shown in FIG. 14, such structure maybe employed downstream of a thermal oxidizer unit processing effluentgases from semiconductor manufacturing operations, so that the gasstream in line 1160 entering the interface structure 1110 is at elevatedtemperature and laden with particulates, such as silica, particulatemetals, and the like, as sub-micron size particles or even largersolids. In such embodiment the upper portion 1126 of the second flowpassage member may be constituted by a sintered metal wall having athickness on the order of 1/16th inch, with an average pore size ofabout 2 microns. The length of the first flow passage member 1112 nay beon the order of 48 inches, with a diameter on the order of 2.5 inches.The corresponding second flow passage member 1124 may correspondinglyhave a length on the order of 13.5 inches, with a diameter on the orderof 4.5 inches, and the outer wall member 1134 may have a vertical lengthon the order of 5.5 inches, with a diameter on the order of 6 inches.

In such system, water may be employed as the liquid medium fromreservoir 1150 which is introduced into interior annular volume 1170 forweep-through of such liquid onto the interior surface 1132 of the upperliquid permeable portion 1126 of the second flow passage member. Theusage of water in such system may be on the order of 0.1-0.3 gallon perminute of operation.

While the invention has been described with reference to illustrativeembodiments, it will be recognized that other variations, modificationand other embodiments are contemplated, as being within the spirit andscope of the invention, and therefore the invention is to becorrespondingly broadly construed with respect to such variations,modifications and other embodiments, as being within the spirit andscope of the invention as claimed.

1. A method for treating the effluent fluid stream from one or moresemiconductor manufacturing process tools, comprising the steps of:removing water soluble gases from the effluent fluid stream; oxidizingat least a portion of the oxidizable components of the effluent fluidstream; and using a wet spray tower comprising a demister mesh packingto remove acidic components from the effluent fluid stream.
 2. Themethod for treating the effluent fluid stream from one or moresemiconductor manufacturing process tools of claim 1, further comprisingremoving particulates in the step of removing water soluble gases fromthe effluent fluid stream.
 3. The method for treating the effluent fluidstream from one or more semiconductor manufacturing process tools ofclaim 2, wherein the step of removing particulates and water solublegases comprises using a wet spray tower.
 4. The method for treating theeffluent fluid stream from one or more semiconductor manufacturingprocess tools of claim 3, wherein said wet spray tower comprises aninert-gas-assisted atomizing nozzle.
 5. The method for treating theeffluent fluid stream from one or more semiconductor manufacturingprocess tools of claim 1, further comprising removing particulates inthe step of removing acidic components from the effluent fluid stream.6. The method for treating the effluent fluid stream from one or moresemiconductor manufacturing process tools of claim 1, wherein the stepof oxidizing comprises the steps of: mixing the effluent fluid streamwith an oxidizer medium; and heating the effluent fluid stream.
 7. Themethod for treating the effluent fluid stream from one or moresemiconductor manufacturing process tools of claim 1, wherein the stepof oxidizing comprises using a catalytic oxidizer.
 8. The method fortreating the effluent fluid stream from one or more semiconductormanufacturing process tools of claim 1, wherein the step of oxidizingcomprises using a thermal oxidizer.
 9. A method for treating theeffluent fluid stream from one or more semiconductor manufacturingprocess tools using a system that includes an oxidizing unit and aquench unit, comprising the steps of: effecting, in the oxidizing unit,the destruction of at least portion of the halogen-containing componentsof the effluent fluid stream using a first hydrogen source and theoxidation of at least a portion of the oxidizable components of theeffluent fluid stream; quenching the effluent fluid stream from theoxidizing unit; recycling water vapor from the quench unit back to theoxidizing unit for utilization as a second hydrogen source to effectdestruction of at least a portion of the halogen-containing componentsof the effluent fluid stream; and removing acidic components andparticulates from the effluent fluid stream.
 10. The method for treatingthe effluent fluid stream from one or more semiconductor manufacturingprocess tools using a system that includes an oxidizing unit and aquench unit of claim 9, wherein the step of effecting oxidationcomprises the steps of: mixing the effluent fluid stream with anoxidizer medium and water vapor; and heating the effluent fluid stream.11. The method for treating the effluent fluid stream from one or moresemiconductor manufacturing process tools using a system that includesan oxidizing unit and a quench unit of claim 9, wherein the step ofeffecting oxidation comprises using a catalytic oxidizer.
 12. The methodfor treating the effluent fluid stream from one or more semiconductormanufacturing process tools using a system that includes an oxidizingunit and a quench unit of claim 9 wherein water vapor is used as thefirst hydrogen source.
 13. A method for treating the effluent fluidstream from one or more semiconductor manufacturing process tools usinga system that includes an oxidizing unit comprising the steps of:removing particulates and water soluble gases from the effluent fluidstream upstream of the oxidizing unit; and quenching the effluent fluidstream downstream of the oxidizing unit using a quench unit aligned withthe oxidizing unit in a single vertical orientation.
 14. The method fortreating the effluent fluid stream from one or more semiconductormanufacturing process tools using a system that includes an oxidizingunit of claim 13, wherein the step of removing particulates and watersoluble gases upstream of the oxidation unit comprises using a wet spraytower including an inert-gas-assisted atomizing nozzle.